Methylglyoxal synthase regulates cell elongation via alterations of cellular methylglyoxal and spermidine content in Bacillus subtilis

Methylglyoxal regulates cell division and differentiation through its interaction with polyamines. Loss of their biosynthesizing enzyme causes physiological impairment and cell elongation in eukaryotes. However, the reciprocal effects of methylglyoxal and polyamine production and its regulatory metabolic switches on morphological changes in prokaryotes have not been addressed. Here, Bacillus subtilis methylglyoxal synthase (mgsA) and polyamine biosynthesizing genes encoding arginine decarboxylase (SpeA), agmatinase (SpeB), and spermidine synthase (SpeE), were disrupted or overexpressed. Treatment of 0.2 mM methylglyoxal and 1 mM spermidine led to the elongation and shortening of B. subtilis wild-type cells to 12.38 ± 3.21 μm (P < 0.05) and 3.24 ± 0.73 μm (P < 0.01), respectively, compared to untreated cells (5.72 ± 0.68 μm). mgsA-deficient (mgsA−) and -overexpressing (mgsAOE) mutants also demonstrated cell shortening and elongation, similar to speB- and speE-deficient (speB− and speE−) and -overexpressing (speBOE and speEOE) mutants. Importantly, both mgsA-depleted speBOE and speEOE mutants (speBOE/mgsA− and speEOE/mgsA−) were drastically shortened to 24.5% and 23.8% of parental speBOE and speEOE mutants, respectively. These phenotypes were associated with reciprocal alterations of mgsA and polyamine transcripts governed by the contents of methylglyoxal and spermidine, which are involved in enzymatic or genetic metabolite-control mechanisms. Additionally, biophysically detected methylglyoxal-spermidine Schiff bases did not affect morphogenesis. Taken together, the findings indicate that methylglyoxal triggers cell elongation. Furthermore, cells with methylglyoxal accumulation commonly exhibit an elongated rod-shaped morphology through upregulation of mgsA, polyamine genes, and the global regulator spx, as well as repression of the cell division and shape regulator, FtsZ.